initial local anesthetic dose with continuous interscalene analgesia

Conditions: Post-operative Pain

Summary: objective: to determine a minimally effective initial local anesthetic bolus required to provide satisfactory analgesia using continuous brachial plexus infusion following arthroscopic shoulder surgery using a double-blind, randomized, study comparing 3 initial doses.

aims: 1. to compare pain ratings and supplemental analgesic requirements at discharge from pacu, 24 hours, and 48 hours and 12 weeks following 5, 10, and 20 ml boluses. 2. to compare adverse events including clinical dysphonia, horner's syndrome, dyspnea, unexpected hospitalization, evidence of local anesthetic toxicity, and hand weakness at discharge from pacu following 5, 10, and 20 ml boluses. 3. to compare impairment in diaphragmatic excursion at discharge from pacu following 5, 10, and 20 ml boluses. 4. to compare patients' satisfaction with analgesia at 24 and 48 hours following 5, 10, and 20 ml boluses. 5. to compare patient rating of functional outcome at baseline and at 12 weeks following 5, 10, and 20 ml boluses. 6. to compare the rate of general anesthesia required following 5, 10, and 20 ml boluses.

Eligibility criteria:
inclusion criteria: * provide written informed consent prior to participation in the study. * is scheduled to undergo arthroscopic rotator cuff repair, defined as arthroscopically assisted repair of any of the muscles or tendons comprising the rotator cuff. * if subject is a female of childbearing potential, have a negative pregnancy test on the day of surgery per standard of care * be at least 18, but not more than 80 years of age * have an asa risk class of i, ii, or iii according to the american society of anesthesiologists (asa). * have the ability to read and understand the study procedures and the use of the pain scales. must have the ability to communicate meaningfully with the study investigator and staff. * be free of other physical, mental, or medical conditions, which in the opinion of the investigator, makes study participation inadvisable. exclusion criteria: * subjects requiring daily opioids equivalent to greater than 40 mg oxycodone for over 2 weeks prior to the study. * has significant preexisting pulmonary (respiratory/breathing) disease, diaphragmatic paralysis or history of phrenic nerve injury (problems with the diaphragm causing breathing difficulties). * has significant medical disease(s), laboratory abnormalities or condition(s) that in the investigator's judgment could compromise the subject's welfare, ability to communicate with the study staff, complete study activities, or would otherwise contraindicate study participation. * has known significant hypersensitivity to opioids, ropivacaine, or the inactive ingredients (excipients) of the study medications. * has known or suspected history of alcohol or drug abuse or dependence within the previous 2 years. * has clinically significant liver disease, or other condition (e.g., alcoholism, cirrhosis, or hepatitis) based on medical history and examination. * has participated in another clinical study (investigational or marketed product within 30 days of surgery.

Keywords: peripheral nerve infusion, continuous brachial plexus block, post-operative pain diaphragmatic paresis